标题： PPMXL目录的ICRS坐标和自行。 结合USNO-B1.0和2MASS 显示英文标题

标题： The PPMXL catalog of positions and proper motions on the ICRS. Combining USNO-B1.0 and 2MASS

摘要： USNO-B1.0和2MASS是使用最广泛的全天候巡天项目。 然而，2MASS完全没有自行数据，而USNO-B1.0只发布了相对自行，而不是绝对（即在ICRS系统上）的自行。 我们通过结合USNO-B1.0和2MASS的天体测量数据，对ICRS系统上的平均位置和自行进行了新的确定。 该星表称为PPMXL {通过 http://vo.uni-hd.de/ppmxl 可以访问目录的 VO-access}，其目标是从最亮的恒星到大约 $V \approx 20$的全天范围都是完整的。 PPMXL包含约9亿个天体，其中约4.1亿个有2MASS的测光数据，目前是最大的ICRS自行数据集合。 作为ICRS的代表，我们选择了PPMX。 最近发布的UCAC3无法使用，因为我们发现其自行系统在-20$^\circ$纬度以北存在底片相关的畸变。 UCAC3作为 $\delta \leq -20^\circ$的中间系统。 自行的典型个体平均误差范围从4毫角秒/年到超过10毫角秒/年，这取决于观测历史。 在2000.0历元的位置平均误差为80至120毫角秒，如果可以使用2MASS的天体测量数据，则为150至300毫角秒。 我们还提供了校正表，以将例如小行星的USNO-B1.0观测转换到ICRS系统。 显示英文摘要

摘要： USNO-B1.0 and 2MASS are the most widely used full-sky surveys. However, 2MASS has no proper motions at all, and USNO-B1.0 published only relative, not absolute (i.e. on ICRS) proper motions. We performed a new determination of mean positions and proper motions on the ICRS system by combining USNO-B1.0 and 2MASS astrometry. This catalog is called PPMXL {VO-access to the catalog is possible via http://vo.uni-hd.de/ppmxl}, and it aims to be complete from the brightest stars down to about $V \approx 20$ full-sky. PPMXL contains about 900 million objects, some 410 million with 2MASS photometry, and is the largest collection of ICRS proper motions at present. As representative for the ICRS we chose PPMX. The recently released UCAC3 could not be used because we found plate-dependent distortions in its proper motion system north of -20$^\circ$ declination. UCAC3 served as an intermediate system for $\delta \leq -20^\circ$. The resulting typical individual mean errors of the proper motions range from 4 mas/y to more than 10 mas/y depending on observational history. The mean errors of positions at epoch 2000.0 are 80 to 120 mas, if 2MASS astrometry could be used, 150 to 300 mas else. We also give correction tables to convert USNO-B1.0 observations of e.g. minor planets to the ICRS system.